Photoelectric device



June 20, 195() y N. c. FULMER 2,512,146

PHoToELEcTRIc DEVICE Filed Oca'c.V 5, 1946 zz es :l

INVENTOR M C. F'LMEE www ATTORNEY Y u c Patented June 20, 1950 PHOTOELECTRIC DEVICE Norman C. Fulmer, Montclair,y N. J., assigner to Westinghouse Electric Corporation, East Pittsl burgh, Pa., a corporation of Pennsylvania Application October 3, 1946,'Serial No. 700,945

This invention'relates to photoelectric devices Iand, more particularly, to such constructed of metal or other non-frangible material.

The principal object of my invention, generally considered, is to produce photoelectric devices or phototubes in which the body of each is ruggedly constructed, as by being made of metal or other non-frangible material, as distinguished from glass as usually employed.

Another object of my invention is to produce phototubes in which the light-sensitive material for the cathode of each is applied to the inside of the vbottom of a rugged metal shell, a Vane-like anode beingv supported by a lead passing through and insulated from said shell.

A further object of my invention is to produce phctotubes'in which the sensitive surface is carried on a rugged metaly portion thereof, a lead passing through said sensitive surface portion and insulated therefrom, and a glass tube extending from the insulating portion around said lead to form along leakage path.

v A still further object of my invention is to produce phototubes in which the casing of each is formed as a cup or shell of metal or other rugged material, which is sealed by a glass window serving to admit light, or other radiation, to the cathode surface therein.

, An additional object of my invention is to produc-e phototubes,V each comprising a rugged metal shell enclosing a cathode formed as a metal disk coated with photo-sensitive material, said shell being closed by a window for admitting radiation to the cathode surface, the anode being formed as conducting strips or wires underlying said window and attached to the metal shell at a distance from the cathode surface.

Another. object of my invention is to produce a 'phototube comprising a rugged shell closed by a glass Window sealed thereto directly adjacent a` structure'formed to function as an anode, the open end of said shell being extended beyond the 'Window to Iform a light shield, and in which said invention.

` Figure 2 is an axial sectional View of the line II-'II of Figure 1, in the direction of the arrows,

p parts being shown in elevation.

16 Claims. (C1. Z50-165) Figure 3 is a plan corresponding to Figure 1, but showing another vembodiment of my invention.

Figure 4 is an axial sectional' View on the line IV-IV of Figure 3, in the direction of the arrows.

Figure 5 is a view corresponding generally to Figure 4, but showing another embodiment of my invention.

Figure 6 isa plan of the combination window and anode of another embodiment of my invention.

Phototubes, as now generally constructed, are fragile devices consisting of an anode anda cathode enclosed within a glass envelope. Because of their fragility, such tubes are usually housed in a protective metal box which has an aperture in one side to allow light or other radiations to enter and impinge on the photoelectric surface of the cathode. Conventional phototubes also generally contain within their glass envelopes considerable spacenot needed for tube operation.

In accordance with my invention, I propose a phototube which, unlike those of present construction, is compact and rugged. The shell of the tube is constructed of non-frangible material, such as metal, andl is cylindrical in shape with a transparent window at one end through which light may enter.

Referring to the drawing in detail, like parts being designated by like reference characters, and rst considering'the embodiment of my invention illustrated injv Figures l and 2, there is shown a' phototube II comprisinga generally cylindrical shell or housing I2 which may be oi" metal, such as Kovarf steel, copper, nickel, or silver. Said shell desirably has a circular end wall I3, integral or separately formed and attached, as shown in one of the figures, the innersurface of which carries a photosensitive material forming the cathode I4. A cylindrical wall I5 extending therefrom, desirably has an annular shoulder I6 providing a seatfor holding a glass window Il parallel tothe end wall '13, and continuing at enlarged diameter beyond said window, as indicated at I3, to provide a light shield.

In the present embodiment the anode I9 is of a Vane-type` construction, with narrow metal strips or wires 2l radiating from a lead 22 which passes through aV hole23 in the end wall I3 of the metal shell. The anode lead 22 is supported and insulated from the shell by a glass seal 24, which closes the hole 23 in the shell bottom wall I3. Integral with the glassseal 24, is a glass tubing'i'nsulator 25, surrounding the anode lead 22 inside o'f the tube shell for the purpose of providing a long leakage path between the anode l5 and cathode Iii. Such an insulating sleeve prevents material deposited in forming the cathode ifi, from making a leakage path to the anode IS. The vane-type of anode construction allows light to easily reach the cathode, and also provides a large area `to collect .electrons/released by .the action of lightion the sensitive surfaceof the cathode lli. The glass window Il' may be sealed to the metal shell in any desired manner, as by induction heating.

The sensitive surface of the cathode M -Inaylbe produced in a conventional .mannenas by deposition of alkali metal, such as cesium,.on an oxidized silver surface. Thus, the shell I2,..if `not-made of silver', mayhave the inner surface of its bottom Wall i3 silver plated before thesensitizing or getter capsule supported on the cylindrical part of the shell E2, is activated. The silver surface is in any Yevent ydesirably carefully cleaned and then etched toprovide an enlarged area and allow finely-divided silver particles to remain to mix .with oxygen and cesium at a later step in 'the process. After 'the getter capsule 26 has'been positioned,'the shell mayhave the Windowil placed, sealed thereto, and the enclosed portion of the shell exhausted through 'tube 28, positioned as shown in one of the figures, While baking 'to puri- 'fy the glass and metal parts. 'Then some purified oxygcnat low pressure, say about 3 millimeters, may-be admitted through said tube 28. The silver plating Son "the surface Yo`f'thebott0m wall 13 may V.then be oxidized asby a jglow'discharge at from 450 'to BUG volts D. C. until the cathode is 'bright emerald jgr'een in color. The remainder of the oxygen is removed 'by evacuating through tube Thelgetter capsule 26 may contain cesiinn-generating'means, such as `a`mixture of c'esium dichrozn'ate 'and a reducing agent such as silicon. The cover o'ithe capsule'may be vof iron or nickel. On aipart of'the 'shell l2, such as on the cylindrivcalisurface, is'an absorbent for excess cesium, such as a 'coating 2'! 'of tin oxide. vThe cesium capsule, being on'the cylindrical surface, may be 'activated 'asby a flame orother'convenient heat- 'ing means, 'directed at the adjacent part ofthe cylindrical portion I5 of theshell.

vThis activationresultsin deposition of cesium on'the oxidized silver `surfacebf the cathode M',

as well as 'otherparts of the tube. As an alternative, cesiurn vapor mayibe'distilled'intothe shell IEthrough the exhaust'tube'i. Theshe'll is'then 'baked on exhaust 'in order vthat the deposited cesium may react with the silver oxide to 4form a highly light-sensitive surface. VThis baking also .removes the cesiuinfrorn'the walls'of thehousing i2 and the window Tl. '1t also removes all but a very thinlayer from the cathode I4. An indication oi when to stop is the brown color o'f the cathode.

The so-called activating ofthe cathode is done by running a glow discharge at about 400 volts in argon at a pressure of about 1'00 microns.

A faint yellow sputtered ilm on the window is f generally an indication of sufiicient activation Excess ces'ium in the shell is absorbed by the tin 4oxide during the baking and activation operaas Kovan steel, copper, nickel, or silver. One end of said shell is desirably closed by a circular shell bottom Wall portion I3, having an outstanding flange 2lia secured to said shell l2*L in any desired manner, as by welding, brazing, or soldering. The cylindrical shell portion i529, extending therefrom, is desirably outwardly offset, as indicated at de, and then desirably provided .with an annular shoulder iSa, forming a seat for a glass Window .ISI-e, and continued at an enlarged diameter beyond said window, as indicated at |821, to provide .a .light Shield.

In the present embodiment, the cathode a vgis formed as afla't thin metal disk, coated with .iight-.sensitive material Ida on the side facing the window Ha. This cathode is supported on a lead SZwhich'passes'through a hole 33 in the circular portion i-l. The lead 32 is supported on, and insulated from, said circular portion by a glass seal 2da which closes the hole in the bottom Wall por- Integral with said glass Aseal 24% is a glass tubing Yinsulator i252 surrounding Vthe llead 32 inside of the shell 12e, for the purpose of'proriding along leakage path betweenthe'electrodes. inthe present embodiment, 'the 'sleeve shown flared to forma circular 4diskportion 34 Lparallel to the cathode -lila,therebymaking it possibleto shorten Ythe 'shell "i221 in this and other'embodiments without decreasing'the'length of the leakage'path A`betvveen'the electrodes.

Such an insulating sleeve lprevents `material deposited in 'sensitizing `the cathode 40a from making a 'leakage lpath to the anode I9a. The

latten'inthis instance, maybeformed by a 'series of conducting stripsor Wires, attachedk electrically 'and mechanically to the metal shell at a desired distanc'efromthe cathodagpreferably directly adjacent the Window "l lagor'as silverlstripes or a silver grid 19'platedonthe inner surface of the glass window Hc, as illustrated `in Figure l6. In he latter rcase, exible 4or -catvvhiskeim means may extend from the-shell `to make electrical connectionwvith saidanode 19a. As a further al- 'tei-native, a -translucent or Asemi-transparent silver nlm `may vbe provided `on lthe inner surface of the window, tobe sensitized `like the member :M and 'function'as the cathode, Athe other electrode functioning .as the anode. Said translucent film may, if desirecL'be superimposed on a grid, like that designated lecjthereby increasing'the icon- `ductivity of the cathode formed. The glass Window .i' may .be sealed to .the 'metal shell in any .desired manner, as by induction'heating.

`The sensitive surface 14a on the cathode Mla may` beproduced in a 'conventional manner, asby deposition of alkali metal, such as cesium, on `an .oxidized surface. Thus,`if the cathode disk is not `made of silver, it may have "the surface, which 'faces .the window 17a, silver plated and treated as described in connection with therst embodiment, before the'senstizing means, such as the getter capsule 26a supported on a cylindrical part of the shell I'Za, is activated` After'the getter capsule `2a has 'been positioned, the shell may 'have the Windowplaced and sealed thereto, and

the enclosed ,portion 'of 'the 'shell vexhausted fthrough'tube 28H. V"ihensome -oxygerrat l'oW pressure, 'sayrabout 3 millimeters may be admitted through said tube 28a. The silver surface'o'fthe cathode disk may "be oxidized 'as Apreviously described in connection with the'nrst embodiment, or in a .conventional manner, the remainder of the oxygen 'being *removed :by exhaustion through The getter capsule "25a may contain -cesium generating means, as in the preceding `embodiment. The shell of the capsule may beof iron or nickel, and fastened ona part of the shell, I2, such as thecylindrical surface of enlarged part Sila.v An absorbent for excess cesium, such as a coating 27a of tin oxide may be von the cylindrical surface. The getter may be activated by a flame, or other convenient heatingmeans, directed at the adjacent part of the cylindrical portion 30a of the shell. This heating resultsin a deposition of cesium on the oxidized silver surface of the cathode 40B, as Well as other parts of the tube. As an alternative, cesium vapor may be distilled in the shell I2 through the exhaust tube 28a. The shell -is then baked on exhaust in order that the deposited cesiurn may react with the silver oxide to form a highly lightsensitive surface. Said baking also acts as described in connection with the rst embodiment, after which activation of the cathode .is effected as previously described, the excess cesium being absorbed by the tin oxide. The tube is then completed, as before.

In the present embodiment the completed phototube is, as an example, shown with a conventional base applied thereto, as by fitting.. a threaded shell portion i 36 thereover untilthe free edge engages the surface of the shoulderv I6a opposite that on which the window I'la is positioned, and securing the free edge thereof to the offset portion 3l!a of the shell I2, in any desired manner, as by soldering or welding. This threaded portion 36 is thus connected to the anode. A center contact 31, insulated from the threaded portion by glass or other insulator 38, is connected to the lead 32 in a conventional manner, as by soldering.

Referring now to the embodiment of my invention illustrated in Figure 5, there is shown a phototube Hb which may correspond with the tube lia of the preceding embodimentfexcept that the lead 32b does not pass through the center of the member I3b, said center being occupied by the exhaust tube 28h, secured thereto, as in the preceding embodiments, by passing through a hole in the shell and having an inner peripheral flange secured to said shell, as by soldering or Welding. Besides this, the insulator h is not flared, as in the second embodiment, but rather extends cylindrically as in the rst embodiment. The glass insulator portion 24b is shown sealing the lead 32D to a metal eyelet 39, having a flange M secured to the circulal` portion I3b around an aperture 33b therethrough as by soldering or welding, rather than fused directly in said aperture. The glass of said insulator portion 24h is shown extending through the eyelet and out of the tube around the lead B2b, as indicated at 43. Except for the diiferent positioning of the getter capsule 26h, and the fact that there is no offset corresponding with that designated a inthe preceding embodiment, the anode members |98 and the window l'lb being the same, the tube Hb may correspond with that of the preceding embodiment. A conventional base, however, is not illustrated.

Instead of making the shell complete with bottom Wall and supported electrode-and then applying the glass window |1b,I may, as an alternative, apply the glass window Ill? and electrode strips E91 to the cylindrical portion I2b and then after assembly 0f the cathode 401 with the bottom wall member I3b and the associated parts, said bottom wall member may be secured in place as by fittingl in-the open end of the shell l2b and securing its flange Zilbxto said shell as bysoldering or welding, as 4indicated at 44.-

.From the foregoing, it` Willzbe seenthat I have providedv'a phototube comprising an enclosing shell which is rugged, as by beingformed yof metal rather than glass, vand in` which; the cathode-sensitizing.material. is applied to a portion of the shell, or to a surface on a disk, for example, insulated and spaced from said shell. A glass tube or ared insulator may be provided around the stem of the electrode which is sep- .arated from the shell, to form a long leakage path between electrodes. A glass window,which may be plated, with or without subsequenttreatment to alsofunction as the cathode or anode, yseals the metal shell after the application of the spaced electrode, and if not plated is desirably disposed adjacent theanode, wherebythe size of the structure is kept small. In embodiments in which the' anode consists `of Wire or conducting strips adjacent, touching, or embedded in the glass window, the material of such is Kovar or other material whose expansion coefficient corresponds sufficiently with that of the tube housing and glass, so that effective sealing results.

The Lempert et al. Patent No. 2,279,831, dated April 14, 1942, is referred to for the formula of Kovarf Although preferred `embodiments of my invention have been disclosed, it will be understood that modications may be made Within the spirit and scope of the appended claims.

I claim: 5

l. -A non-frangible photoelectric .device compris'ing a non-frangible main :container portion having a bottom wall member, an extension of section different from that of said 'main container portion and providing a shoulder adjacent its junction therewith, a lead passing through said wall member and insulated therefrom, an electrode member in said container and' supported on said lead in spaced relation with respect to Vsaid bottom' wall member, one of said fmembers carrying' photo-sensitive material to function as a cathode, and a glass window sealed to said extension adjacent said shoulder to admit light t0 said sensitive material.

2. A photoelectric device comprising a nonvfrangible container having a generally flat bottom metal wall member, a lead passing through said Wall member and insulated therefrom, an electrode. member in said-container, disposed generally parallel to said bottom wall member, and supported on said lead in spaced relation with respect to said Wall member, the metal wall member carrying photo-sensitive material to function as a cathode, and a glass window seallng said container in position'to admit llight to said `vsensitive material.

3. A photoelectric device comprising a nonfrangible container with a metal end wall portion, a lead passing through said end wall portion and insulated therefrom, al thin metaly dis'k inside said container and supported on 'said lead, a glass window closing the other end of saidv container and -positioned to admit light to said disk, photosensitive material on the surface of said disk facing said window, and conducting portions traversing said container adjacent said window to functionas an anode.

4. A photoelectric device comprising a metal container having a generally flat bottom wall member,v a" lead passing centrally through said rbottcm'wall. and insulated therefrom, anelec- :trode .member in said Ycontainer and supported on said lead inspaced generally parallel :relation --wit-h respect to .said .bottom ywall member, one of 'said members :carrying photo-sensitive';mate rial to function as a cathode,.and..a glass Window v.sealing .said container and fpositionedcto .admit light .to .said .sensitive material.

15. .A photoelectric .device .comprising a metal .container having a ,generally flat metal bottom wall zmember, :a lead .passing through said Wall member, .an insulator formed asa .tube surrounding said lead .to provide for .a long leakage path, said `insulator also serving to .secure said lead .to .said container, an electrode .member in said `container, disposed generally parallel to said .bot- .tom Wall member, and .supported :on said .'lead .in -spaced .relation with respect to ysaid bottom wall member., one of said members carryingphotolsensitive .material to 4function as a cathode, and v:a glass Window lsealing .said container and positioned to admit light vto said sensitive material.

6. A photoelectric .device comprising a nonfrangible container having ,a bottom wall member, .a lead passing lthrough said wall member, an insulator .closing .a hole in said wall member and through which said lead passes, an electrode .member in said container, said insulator being extended towards said .electrode member and flared to provide a long leakage path disk adiacent thereto, said electrode member being .supported .on said lead in spaced rrelation with respect to saidbottom Wall member, one of :said members carrying photo-.sensitive material to function as a cathode, and a glass Windowsealing `said container` in position to admit light to said :sensitive material...

7. A photoelectric device comprising a .metal container having :a generally flat metal bottom wall member, .a lead `.passing through -said 'Wall member and insulated therefrom, an electrode :member in said :container and supported on said lead in vspaced -generally parallel relation to :said bottom wall member, a getter capsule device `.mounted :on the inside of said container in a position convenient for activation by external :heat for supplying photo-sensitizing material to cause one of the lmembers to function as a cathode, and a glass YWindow sealing said container and positioned to'admit light to said cathode.

-8. A photoelectric device comprising a metal container havingwa generally flat bottom wall rportion, Lan :exhaust :tube .extending through :approximately-'fthe .center of said portion, .an :aperture between said yexhaust `tube and `the rim of said bottom @wall member, an eyelet having a l flange secured :to said iwall vmember :around said 'aperture and =a cylindrical Vportion extending inwardly from said. Wall member, a lead passing through -sa'id eyelet, insulating material .sealing said lead in said eyelet, an electrode member in said container and .supported on .said lead in spaced relation -Lto said `bottom wall'member, one vof said members carrying photo-sensitive vmate- .rial to functionraska cathode, and a glass vWindow sealing said container in -position to--admit light to :said :sensitive :material 9. A .photoelectric device comprising aymeta-l container having a :bottom Wall member, a flead passing throughlsaid wall member and insulated therefrom, a vane-type anode member supported in said container by said lead and spaced with respect -to rbottom-iwalbmember, :said 'bottom wall .member having an inner oxidized silver 4surface .and carrying aphoto-'sensitive material to function asa cathodeandfa glasswimdowsealing :said

lcontainer and positioned to admit light to said cathode.`

10.. A zphotoelectrc device comprising a metal container having a metal bottom Wall member, a. lead .passing through said wall member, Aan .insulator betweensaid lead and Wall member and lincluding a tube :portion around the former to provide a 'long leakage path, an electrode mem- .ber in said .container :and supported on said lead vin spaced relation .with respect to said bottom yvvall'member., said lead-supported electrode having .a surface of .oxidized silver `facing away from .said ,bottom wall member .and coated with photo- 'sensitive material to function as a cathode, an anode structure traversing `said container over said cathode, and agglass window sealing said container and disposed directly adjacent said anode structure.

`ill. A generally -cylindrical `pllotoelectric device comprising a Ymetal container having an annular shoulder .andcontinuing at enlarged diameter :beyond said shoulder, a metal `bottom wall member closing one end .of said container, a lead passing .through said `Wall member vand insulated therefrom, an electrode member in said con- 4tainerand supported on said lead in spaced relation .with Arespect to `said bottom wall member, one of said 'members carrying vphoto-sensitive material to function as a cathode, and a glass window .sealing .said container, .seated on said shoulder, and positioned `to admit light .to said ,sensitive material, the Wall of said container v`which extends beyond said shoulder and supported window, forming a .light shield.

l2. 'A photoelectric device comprising a genierally cylindrical metal .container having a ,gen-

erally circular bottom vvall member at one end Vand flanged adjacent its other end to provide a shoulder, .a lead lpassing through said Wall and insulated therefrom, an electrode member in said .container' andfsupported on said lead in spaced relation iwith respect to said bottom wall member, :one of said members carrying photo-sensitive .materialito .function las. a cathode, -a glass window sealing Said container and .positioned on said shoulder-to admit light to said cathode, and a base .comprising a threaded shell in which said rcontainerffits Aand `a center contact, the free edge .of saidshell engaging the .surface of said shoul- .der opposite that on which the window is posiftioned, .and means securing said container to :said shell and said lead to ls aid center contact.

1'3. A photoelectric device comprising a nonkfrangible ycontainer formed Withan annular ledge and having a bottom Wall member, a lead passing .through said Wall member and insulated therefrom, .an electrode member in said container .and supported on said 'lead in spaced re- `lation with Jrespect to said bottom wall member, and a fiat glass window member v/ith its edge seated on said ledge `and sealing said container, `one of said members carrying "photo-,sensitive `material to function as :a cathode and said glass VWindovv .member .servi-ng. to admit light to said .photo-sensitive material.

14. A photoelectric device comprising za non- 'frangible l'container having la Ymetal -bottom wall rmember, a lead passingthrough said Wall member and insulated therefrom, -an electrode member in said container .and supported on said lead in :Spacedrrelation 'with respect to said bottom wall member, said electrode member carrying .photosensitive material to function as a cathode, a fglass Window sealing said container and positioned to admit light to said photo-.sensitive material, and a conductive grid formed on the inner surface of said Window and electrically connected to said container to function as an anode.

15. A photoelectric device comprising a nonfrangible container having a metal bottom Wall member, a lead passing through said wall member and insulated therefrom, an electrode member in said container, disposed generally parallel to said bottom wall member, and supported on .said lead in spaced relation with respect to said bottom Wall member to function as an anode, a glass Window, disposed generally parallel to? said bottom wall member, sealing said container, a very thin translucent film of silver on the inner surface of said window, the inner surface of said film being treated and coated to form a photosensitive surface functioning as a cathode, and means connecting said surface to said container.

16. A radiant energy device comprising a container having a main enclosure portion, a cylindrical extension of diierent diameter from said 10 main portion, providing an annular shoulder adjacent the junction between said main and eX- tension portions, a lead passing through one wall of said container and insulated therefrom, an electrode member in said container and supported on said lead, and a glass element sealing said container and seated on said shoulder.

NORMAN C. FULMER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,881,521 Gstyr et al Oct. 11, 1932 1,885,819 Geffcken et al. Nov. 1, 1932 1,900,577 Moore Mar. 7, 1933 2,029,414 De Boer et al. Feb. 4, 1936 2,306,376 Beuchon Dec. 29, 1942 2,444,915 Cade July 13, 1948 

